In one lens interchangeable type camera system, an image capturing apparatus (referred to as a “camera body” hereinafter) provides an image capturing process, lens controls, and image recording, and a lens apparatus (referred to as an “interchangeable lens” hereinafter) drives a lens and an aperture stop in accordance with a control command from the camera body. In this camera system, the control command is communicated from the camera body to the interchangeable lens and lens information is communicated from the interchangeable lens to the camera body via a communication system for mutual communications of information.
A digital camera system among the interchangeable type camera systems is demanded for a smooth lens control in synchronization with an image capturing period in motion image capturing and in live-view display. For this purpose, it is necessary to synchronize image capturing timing of the camera body with control timing of the interchangeable lens, and the camera body needs to complete receiving the lens information necessary for the lens control and transmitting the control command to the interchangeable lens within the image capturing period.
A data amount of the lens information to be received by the camera body from the interchangeable lens increases due to sophisticated image capturing controls and a larger data amount needs to be communicated within a shorter time period due to a shortened image capturing period (or a higher frame rate).
Patent Literature (“PLT”) 1 discloses a data communication system that includes an initial communication mode with the fixed number of communication words used to recognize a connection state between the camera body and the interchangeable lens and a controlled function in the interchangeable lens and a control communication mode with the variable number of communication words used to control a function of the interchangeable lens. In this communication system, the camera body determines the number of communication words in the control communication mode in accordance with the controlled function in the interchangeable lens obtained in the initial communication mode, and transmits information of the number of communication words to the interchangeable lens after the communication mode is switched. Thus, a communication data amount is reduced between the camera body and the interchangeable lens by limiting the communication data to the controlled function in the interchangeable lens and by eliminating unnecessary communication data.